<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>数组的新增</title>
</head>
<body>
<script>
    var  userName = ['tom','fank','1'];
    // userName[3]=['6'];    //数组的新增
    // userName.push('math');   //在数组的结尾添加元素
    userName.unshift('math');    //在数组的开头添加元素
    console.log(userName)
</script>
</body>
</html>